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Help/Pressure/Engine Modes

Engine Modes

Pressure includes five compression voices built around distinct response topologies. The Mode selector switches the entire compression algorithm - not just a filter or saturation flavor, but the fundamental gain reduction behavior.

MIX - VCA

Clean bus glue character

The VCA engine is Pressure's cleanest glue voice. It's punchy, versatile, and a strong default choice for mix bus and group compression.

Ratio range: 2:1 to 8:1 (PRESSURE driven)

Attack: 0.1-100 ms (clamped). Scales from 30 ms at P=0 to 1 ms at P=1.0.

Release: 10-2000 ms (clamped). From 1200 ms at P=0 to 100 ms at P=1.0.

Knee: Scales inversely with ratio - wide (12 dB) at low PRESSURE, narrow (3 dB) at high. The result is gentle control at low settings and firmer shaping as you lean on it.

Sidechain HPF:Controlled by TONE. tone² × 60 Hz, range 20-120 Hz (reduced from 150/300 in v1.2 to keep bass in detection per Pro-C 2 Bus defaults).

When to use MIX

  • • Stereo bus / mix bus glue
  • • Group buses (drums, vocals, strings)
  • • Gentle cohesion on submixes
  • • Parallel compression blends

INST - FET

Fast, assertive character

The FET engine is the fastest, most assertive voice in Pressure. At high PRESSURE values, it enters an extreme ratio mode for intentionally colorful control.

Ratio steps:4:1 (P<60%), 8:1 (P<80%), 12:1 (P<92%), 20:1 (P<97%), All Buttons In / 21:1 (P≥97%)

Attack:20-800 μs (microseconds, not milliseconds). This is the fastest attack envelope in Pressure.

Release:50-1100 ms. Follows a V-shaped curve: shortest at P=0 and P=1.0, longest at P=0.5. Formula: 50 + 400 × P × (1-P) ms.

Input drive: Threshold maps to inverted input gain so higher PRESSURE pushes more level into the detector. More drive means more compression and more attitude.

Saturation: Two-stage FET saturation adds harmonic content. Output gain automatically compensates for input drive and saturation gain.

Sidechain HPF: None. The FET engine does not use sidechain filtering.

When to use INST

  • • Electric and acoustic guitar
  • • Bass guitar (drive and sustain)
  • • Synths and keyboards
  • • Aggressive vocal compression
  • • All Buttons In mode for extreme parallel effects

VOCALS - Opto

Smooth optical character

The Opto engine uses a smooth, optical-style response. It has no fixed ratio - compression increases naturally with signal level, creating musical dynamics control.

Ratio:Continuously variable from 2:1 to 12:1. Not stepped - the detector's sensitivity creates an emergent ratio that varies with signal level.

Peak Reduction: Maps from PRESSURE via threshold. At P=0.5, peak reduction is ~30 (moderate); at P=1.0, it reaches 60 (heavy).

Attack/Release: Hardwired in the optical cell model - not user-adjustable. The optical element has inherently smooth, program-dependent timing.

Tube warmth: Subtle, musical even-harmonic warmth from the tube stages, deepening as compression increases. The DRIVE knob adds more of this tube colour as you push it, while the optical gain reduction itself stays clean.

TONE behavior:Controls emphasis (not sidechain HPF). Maps directly to the optical cell's emphasis parameter.

When to use VOCALS

  • • Lead and backing vocals
  • • Voiceover and dialogue
  • • Podcast and streaming voice
  • • Any source needing transparent, smooth leveling

DRUMS - Dynamics

Direct, hard-knee character

The Dynamics engine is direct and precise - it controls dynamics without adding much color. Its defining characteristic is a permanently hard knee (0 dB).

Ratio range: 2:1 to 8:1

Attack: 3-30 ms. Slightly slower than VCA to preserve drum transients.

Release: 100-300 ms. Auto-release tuning set separately for program-dependent recovery.

Knee: Always hard (0 dB). No soft-knee option.

Sidechain HPF:Controlled by TONE. tone² × 120 Hz, range 20-120 Hz. Protects kick drum from triggering excessive compression.

When to use DRUMS

  • • Individual drum tracks (snare, kick, toms)
  • • Drum bus and room mics
  • • Percussion and programmed beats
  • • Any source where transient preservation is critical

MASTER - VariMu

Wide-knee mastering character

The VariMu engine is Pressure's widest, slowest voice for gentle mix control. Its always-wide knee and slower release times make compression nearly invisible while adding warmth and cohesion. Its tube saturation is anti-aliased, so the richest settings stay clean without raising the oversampling mode.

Ratio range: 2:1 to 8:1. Variable-mu ratio modulation in the engine makes effective ratio change with signal level.

Attack: Clamped 0.2-30 ms. Lower PRESSURE stays quicker; higher PRESSURE expands into slower mastering-style timing.

Release: 300-5000 ms. This is the longest release range in Pressure and is tuned for broad, low-drama control.

Knee: Always wide (10-24 dB, enforced minimum 10 dB).

Tube warmth: Even-harmonic warmth that adds perceived loudness and body without raising the actual level; the TONE knob shapes how much.

Sidechain HPF:Controlled by TONE. tone² × 80 Hz, range 20-160 Hz (reduced from 120/250 in v1.2 to keep the detector more mid-inclusive).

When to use MASTER

  • • Master bus sweetening
  • • Stereo mix glue (mastering context)
  • • Orchestral and cinematic material
  • • Any source where warmth and transparency matter

Engine Comparison

VCA

Max Ratio
8:1
Fastest Attack
1 ms
Knee
Variable
SC HPF
Yes
Coloration
Clean

FET

Max Ratio
21:1
Fastest Attack
20 μs
Knee
6 dB fixed
SC HPF
No
Coloration
Colorful

Opto

Max Ratio
12:1
Fastest Attack
Fixed
Knee
N/A
SC HPF
No
Coloration
Warm

Dynamics

Max Ratio
8:1
Fastest Attack
3 ms
Knee
Hard (0 dB)
SC HPF
Yes
Coloration
Transparent

VariMu

Max Ratio
8:1
Fastest Attack
0.2 ms
Knee
Wide (10-24 dB)
SC HPF
Yes
Coloration
Warm

For exact PRESSURE curve values at P=0, P=0.5, and P=1.0, see PRESSURE Control.

PRESSURE ControlControls Reference